I will be attending(co-organising) both Conception 2010 (Jan 2010) and Indiecon 2009... (Nov 2009)
Both are run at the same site in the South of England.
In my experience, at cons it not so much a problem finding players...but finding the scenarios to suit. Con games are generally 3-4 hours long. With rolemaster that means 1-3 combats tops assuming all are experienced players.
I have run a few rolemaster games as convention scenario, all historical rather than fantasy (avoids spells..
)
To be able to run at either (which I am very willing to try) I'd need a scenario, pre-gens and some simplified charts (or at least those used in the scenario).
The most important thing is the Pre-gen character sheets... less is more and they need to be attractive, dump excess stats and skills... just present the important skills (and bonuses)... and defaults for the various skill groups (Which should double for attribute checks etcs). Should be able to manage to present the character on 2 x a4 sheets maximum including background, relationship with other characters etc.
Any more than that and your players will be spending longer trying to find the info than playing the games.